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EL2245

Dual/Quad Low-Power 100MHz Gain-of-2 Stable Op Amp

Intersil 

EL2245, EL2445

Burn-In Circuit (Per Amplifier)

ALL PACKAGES USE THE SAME SCHEMATIC

Applications Information

Product Description

The EL2245 and EL2445 are dual and quad low-power

wideband monolithic operational amplifiers built on Elantec's

proprietary high-speed complementary bipolar process. The

EL2245 and EL2445 use a classical voltage-feedback

topology which allows them to be used in a variety of

applications where current-feedback amplifiers are not

appropriate because of restrictions placed upon the

feedback element used with the amplifier. The conventional

topology of the EL2245 and EL2445 allows, for example, a

capacitor to be placed in the feedback path, making it an

excellent choice for applications such as active filters,

sample-and-holds, or integrators. Similarly, because of the

ability to use diodes in the feedback network, the EL2245

and EL2445 are an excellent choice for applications such as

fast log amplifiers.

Power Dissipation

With the wide power supply range and large output drive

capability of the EL2245 and EL2445, it is possible to exceed

the 150°C maximum junction temperatures under certain

load and power-supply conditions. It is therefore important to

calculate the maximum junction temperature (TJMAX) for all

applications to determine if power supply voltages, load

conditions, or package type need to be modified for the

EL2245 and EL2445 to remain in the safe operating area.

These parameters are related as follows:

TJMAX = TMAX + (ΘJA × PDMAXTOTAL)

where:

PDMAXTOTAL is the sum of the maximum power dissipation

of each amplifier in the package (PDMAX). PDmax for each

amplifier can be calculated as follows:

PDMAX

=

2 × VS × ISMAX + (VS

–

VOU

TM

A

X

)

×

-V----O----U----T----M-----A----X--

RL

where:

TMAX = Maximum ambient temperature

θJA = Thermal resistance of the package

PDMAX = Maximum power dissipation of each amplifier

VS = Supply voltage

ISMAX = Maximum supply current of each amplifier

VOUTMAX = Maximum output voltage swing of the

application

RL = Load resistance

To serve as a guide for the user, we can calculate maximum

allowable supply voltages for the example of the video cable-

driver below since we know that TJMAX = 150°C, TMAX =

85°C, ISMAX = 7.6mA per amplifier, and the package θJAs

are shown in Table 1. If we assume (for this example) that we

are driving a back-terminated video cable, then the

maximum average value (over duty-cycle) of VOUTMAX is

1.4V, and RL = 150Ω, giving the results seen in Table 1.

TABLE 1.

PART PACKAGE ΘJA

DUALS

MAX PDISS

@TMAX

MAX VS

EL2245CN PDIP8 100°C/W 0.650W @85°C ±16.6V

EL2245CS

SO8

160°C/W 0.406W @85°C ±10.5V

QUADS

EL2445CN PDIP14 81°C/W 0.802W @85°C ±11.5V

EL2445CS SO14 120°C/W 0.542W @85°C ±7.5V

Single-Supply Operation

The EL2245 and EL2445 have been designed to have a

wide input and output voltage range. This design also makes

the EL2245 and EL2445 an excellent choice for single-

supply operation. Using a single positive supply, the lower

input voltage range is within 100mV of ground (RL = 500Ω),

and the lower output voltage range is within 300mV of

ground. Upper input voltage range reaches 4.2V, and output

voltage range reaches 3.8V with a 5V supply and

RL = 500Ω. This results in a 3.5V output swing on a single

5V supply. This wide output voltage range also allows single-

supply operation with a supply voltage as high as 36V or as

low as 2.5V. On a single 2.5V supply, the EL2245 and

EL2445 still have 1V of output swing.

Gain-Bandwidth Product and the -3dB Bandwidth

The EL2245 and EL2445 have a bandwidth at gain-of-2 of

100MHz while using only 5.2mA of supply current per

amplifier. For gains greater than 4, their closed-loop -3dB

bandwidth is approximately equal to the gain-bandwidth

product divided by the noise gain of the circuit. For gains

less than 4, higher-order poles in the amplifiers' transfer

9

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